Referring to FIG. 1, an electronic device 102 uses a multi media card (MMC) 104 that stores large amounts of audio and video data, as described at the web-site http://www.mmca.org. The electronic device 102 includes a slot 106 for holding the MMC 104. The electronic device 102 may be a cell phone, a PDA (personal digital assistant), a digital camera, etc. The MMC 104 typically has about 4 GB (giga-bytes) of memory capacity.
However, an electronic device may require higher memory capacity than 4 GB such as when the electronic device 102 runs multiple applications. FIG. 2 shows a block diagram of the electronic device 102 having a first application 108 and a second application 110 accessing relatively high amount of data. The two applications 108 and 110 reside in a host system 112 of the electronic device 102. The host system 112 also includes a CPU (central processing unit) 114 having a first MMC (multi media card) host controller 116 and a second MMC host controller 118.
Because the first and second applications 108 and 110 use higher than 4 GB of data, the electronic device 102 includes a first MMC (multi media card) 120 and a second MMC (multi media card) 122. The first MMC 120 includes a first MMC slave controller 124 that performs memory operations on a first memory module 126 having 4 GB of memory capacity. The second MMC 122 includes a second MMC slave controller 128 that performs memory operations on a second memory module 130 having 4 GB of memory capacity.
The electronic device 102 also includes first interface pins 132 for exchange of signals between the first MMC host controller 116 and the first MMC 120, and second interface pins 134 for exchange of signals between the second MMC host controller 118 and the second MMC 122.
FIG. 3 shows a block diagram of an electronic device 140 having just one application 108 that requires higher memory capacity than 4 GB. Thus, the electronic device 140 uses multiple MMC's 120 and 122. Elements having the same reference number in FIGS. 1, 2, and 3 refer to elements having similar structure and/or function.
In either case of FIGS. 2 and 3, the host controllers 116 and 118 generate 48-bit commands with 32-bits for addressing according to the current standard for generating commands for multi media cards, as specified at the web-site http://www.mmca.org. Thus, each MMC 120 or 122 has a respective memory module 126 or 130 with approximately 4 GB (i.e., 232) of data.
However, use of the multiple MMC's 120 and 122 as in FIGS. 2 and 3 is inefficient with higher costs for forming multiple slots and the multiple interface pins 132 and 134 in the electronic device, and higher cost for the multiple MMC's 120 and 122. In addition, the electronic device using the MMC's is typically a portable device such that multiple MMC's undesirably increase the size of the portable electronic device.
Thus, an efficient mechanism is desired for increasing memory capacity of the MMC. A new command standard with commands having higher than 32-bits for addressing may be a solution. However, approval and adoption of a new command standard takes time. In addition, implementation of a new command standard may require hard-ware change in the host controllers 116 and 118 which would typically require large effort.